all.bash: use locally installed version of prettier

Switching all.bash to use a locally installed version
of prettier to remove the expectation that it is
globally installed.

Change-Id: Ib3bf0da16b3d8bfad817be693fff62776f6e99da
Reviewed-on: https://go-review.googlesource.com/c/pkgsite/+/313529
Trust: Jamal Carvalho <jamal@golang.org>
Run-TryBot: Jamal Carvalho <jamal@golang.org>
Reviewed-by: Julie Qiu <julie@golang.org>
TryBot-Result: kokoro <noreply+kokoro@google.com>

all.bash

@@ -201,10 +201,10 @@ run_prettier() {
   if [[ $files = '' ]]; then
     files=$prettier_file_globs
   fi
-  if [[ -x "$(command -v prettier)" ]]; then
-    runcmd prettier --write $files
+  if [[ -x "$(command -v npx)" ]]; then
+    runcmd npx prettier --write $files
   else
-    err "prettier must be installed: see https://prettier.io/docs/en/install.html"
+    runcmd ./devtools/docker_nodejs.sh npx prettier --write $files
   fi
 }